The effect of geometry on the micromechanical behaviour of campaniform sensillum biomimetic structure as strain sensor

Abstract

Campaniform sensillum is a very sensitive strain sensing organ even though it is small in size. Various geometrical features which could contribute to strain sensing detection as being employed by the insect sensing organ were investigated. This study was carried out with the objective to investigate the effect of the geometry on the mechanical behaviour of campaniform sensillum by using biomimetic structures. The four structures were modelled as chip block, chip block with through hole, chip block with flat membrane-in-recess, and chip block with dome-shaped membrane to represent the features of campaniform sensillum. The potential of these structures as new sensing mechanism for strain sensing were evaluated using the finite element software as the result could be predicted together with associated strain and displacement. The results showed that hole and dome shape structure features were the main features that contributed to the excellent sensing behaviour of the mimetic structure. The sensing mechanism was started with the localization of strain around the hole several times higher than the applied load (first amplifier), before it was further transduced and amplified by the dome structure that acted as a transducer and second amplifier. Compared to the previous biomimetic structure of campaniform sensillum, the suggested biomimetic with the dome shape structure performed better by increasing the strain by a strain concentration factor of 5.45, whereas the structure with hole was 1.03 lower. Besides, combination of these features makes the devices to have higher sensitivity in term of a ratio of output signal to the input signal. In addition, the output signal in the form of vertical displacement was also improved. This makes the structure act efficiently to deliver the information related to strain detection. The obtained understanding can be applied in the design of highly miniaturized strain sensor for medical application.